CN107640775B - Method for preparing ZSM-5 molecular sieve by using solid waste - Google Patents

Abstract

The present invention relates to a method for preparing ZSM-5 molecular sieve by utilizing solid waste, in particular to providing all or part of all or part of the synthesis of ZSM-5 molecular sieve by using solid wastes such as rice husk ash, iron tailings and gold tailings as raw materials Silicon source and aluminum source, and the preparation process for synthesizing ZSM-5 molecular sieve without the participation of solvent and NaOH at the same time. The silicon source, aluminum source, Na ₂ CO ₃ ∙10H ₂ O, template agent or crystal seed are mixed and directly placed in a reactor for constant temperature crystallization to obtain ZSM-5 molecular sieve. This method applies Na ₂ CO ₃ ∙ 10H ₂ O to the In the process of synthesizing ZSM-5 molecular sieve from solid waste as raw material, there is no secondary pollution during the synthesis process. The invention uses solid wastes such as rice husk ash, iron tailings, gold tailings and other solid wastes as raw materials to synthesize ZSM-5 molecular sieves by a solvent-free method. The process is simple and the scope of application is wide, which can not only alleviate the environmental problems caused by solid wastes, but also High value-added utilization of solid waste can be achieved.

Description

A method for preparing ZSM-5 molecular sieve by using solid waste

technical field

The invention belongs to the field of molecular sieve preparation and environmental protection. Specifically, rice husk ash, iron tailings and gold tailings are used to provide all or part of the silicon and aluminum sources required for the synthesis of ZSM-5 molecular sieves, and at the same time, without the participation of solvents and NaOH, the synthesis of ZSM-5 containing hierarchical pores A method for preparing ZSM-5 molecular sieve by using solid waste of molecular sieve.

Background technique

Since ZSM-5 molecular sieve was first reported by American Mobil Corporation in 1972 (USP3702886), due to its unique pore structure and shape-selective catalysis, it has been applied in many oil refining and chemical processes, and its preparation method has been continuously improved. From the initial synthesis using organic amine template agent to the subsequent synthesis without amine, the manufacturing cost of ZSM-5 is significantly reduced. The application field of -5 molecular sieve is expanding continuously. For example, none of the early fluid catalytic cracking (FCC) catalysts used in the refining industry used ZSM-5 molecular sieves, while most of today's FCC catalysts have ZSM-5 molecular sieves added to improve catalyst performance and thus product distribution. Since FCC catalyst is a kind of catalyst with great demand, the annual consumption in the Chinese market alone reaches tens of thousands of tons, which leads to an increase in the demand for ZSM-5 molecular sieve, and also requires further reduction of ZSM-5 molecular sieve. Cost of production.

On the other hand, the role of zeolite molecular sieves, including ZSM-5 molecular sieves, in catalysts such as FCC catalysts is as active components, and good dispersion of active components is very important for catalysts, which can improve the active components. the utilization efficiency of points. An important measure to improve the dispersion of active molecular sieve components in the catalyst is to use molecular sieve products with as small a crystal size as possible. It is well known that nanocrystals or molecular sieves incorporating mesopores can optimize molecular sieves due to the increase in surface area, reactive sites for reactions, and molecular diffusion, providing additional potential in fields such as catalysis and adsorption applications, so nanocrystalline molecular sieves are useful for the fabrication of high-performance catalysts. necessary. However, the size of the existing solvent-free synthesis of molecular sieve crystals is usually in the range of several microns, so it is a huge challenge to use the solvent-free method to synthesize nanocrystalline molecular sieves.

The usual method for preparing ZSM-5 molecular sieve is to use an alkaline silica-alumina gel system to synthesize it. The system consists of sodium oxide, aluminum oxide, silicon oxide and water. The silicon source used for synthesizing raw materials is generally water glass, silica gel, etc., and the aluminum source is generally aluminum sulfate, sodium aluminate, etc. Before the 1980s, quaternary ammonium salts or other organic amines were generally used as templates to synthesize ZSM-5 molecular sieves (referred to as "amine method"). The technology of synthesizing ZSM-5 molecular sieve by using ZSM-5 molecular sieve seed crystal (ie "seed crystal method" or "amine-free method") makes the preparation cost of ZSM-5 molecular sieve significantly reduced.

The synthesis process of ZSM-5 molecular sieve basically adopts hydrothermal method, dry glue conversion method, solvent-free method and so on. The hydrothermal synthesis system needs to contain a large amount of alkaline solution, and the raw materials need to be stirred and aged before the synthesis process in the reactor, which reduces the synthesis efficiency of molecular sieves. The dry gel conversion method is a method of solid-phase synthesis of molecular sieves, including gas-phase conversion method and steam-assisted method. It is necessary to mix silicon source, aluminum source and water to prepare gel, and the dry gel after water removal is used to prepare molecular sieve. The above methods cannot completely avoid the use of solvents in the process of preparing ZSM-5 molecular sieves, generate a large amount of alkali-containing wastewater and reduce the space utilization rate of molecular sieve synthesis equipment. Solvent-free method means that no solvent is used in the preparation process of molecular sieve. At present, the solvent-free method mainly uses pure chemical reagents as raw materials. , The utilization rate of equipment is high, but the synthetic raw materials contain NH ₄ F, NH ₄ Cl and other substances that are harmful to the environment, which are not suitable for large-scale industrial applications, and there is no solvent-free synthesis of molecular sieves using solid waste as raw materials. report.

SUMMARY OF THE INVENTION

In order to solve the above-mentioned problems, the main purpose of the present invention is to provide a kind of solid waste that utilizes cheaper and more extensive sources of raw materials as synthetic raw materials, and uses a solvent-free method to mix the raw materials and directly put them into a reaction kettle and seal them at a certain temperature. Synthesis, there is no NH ₄ F, NH ₄ Cl and other substances harmful to the environment in the raw materials, and a green and low-cost method for synthesizing the ZSM-5 molecular sieve with nanocrystalline hierarchical pores is realized.

The raw materials include solid wastes such as rice husk ash, gold tailings and iron tailings. The content of SiO2 in rice husk ash reaches about 90%, and it is amorphous, which can be directly used as a silicon source to prepare ZSM-5 molecular sieve; iron tailings in the raw material The composition of and gold tailings mainly contains quartz, albite, potassium feldspar, anorthite, magnetite, pyrite, cordierite, talc and illite. The composition of gold tailings and iron tailings is complex and contains many silicate minerals and impurities of magnetite and pyrite, the content of _SiO2 accounts for more than 60%, and the silicate minerals in gold tailings and iron tailings need to be activated.

The technical scheme of the present invention is: a method for preparing ZSM-5 molecular sieve by utilizing solid waste, the method specifically comprises the following steps:

Step 1: take the solid waste as the silicon source, mix the silicon source, sodium carbonate decahydrate, aluminum source material and template agent according to a certain ratio, and mix and grind for 1-10 minutes;

Step 2: Put the mixture obtained in Step 1 into a stainless steel reactor, heat up to 100-200°C, and crystallize for 3-96 hours. After the crystallization is completed, rapidly cool, wash, and dry the filter cake to obtain a filter cake containing a hierarchical pore structure. ZSM-5 molecular sieve.

Further, the ratio of the silicon source, sodium carbonate decahydrate, aluminum source material and template agent is: n(TPABr)/n(SiO ₂ )=0.1-2.0; n(Na ₂ CO ₃ ·10H ₂ O)/n (SiO ₂ )=0.1 to 10; n(SiO ₂ )/n(Al ₂ O ₃ )=20 to +∞.

Further, the solid waste is rice husk ash, iron tailings or gold tailings. When iron tailings and gold tailings are used, the iron tailings and gold tailings need to be activated now.

Further, the activation treatment process is as follows: the gold tailings and the iron tailings are activated by means of alkali sintering, n(NaOH)/n(SiO ₂ )=1～4, the activation treatment temperature is 200～1000°C, and the activation The treatment time is 1 to 10 hours. The activated alkali sintered product is mixed with water and stirred for 50-70 minutes, the product is divided into water-soluble substances and water-insoluble solids, the solution pH is directly adjusted without separation of solid and liquid, and the solution is left standing for 6 to 24 hours at 80°C Dry at constant temperature to obtain solid powder.

Further, the composition of the iron tailings or gold tailings: the composition of the iron tailings or gold tailings mainly contains quartz, albite, potassium feldspar, anorthite, magnetite, pyrite, and cordier. Bluestone, talc and illite.

Further, the iron tailings and gold tailings are not subjected to acid leaching and purification treatment before activation, so as to avoid the generation of acid-containing waste liquid.

The synthetic ZSM-5 molecular sieve and preparation method provided by the invention have the following characteristics:

(1) The range of raw materials for synthesizing ZSM-5 molecular sieve by solvent-free method was expanded, new uses were found for solid wastes such as rice husk ash, iron tailings and gold tailings, and the cost of raw materials for preparing ZSM-5 molecular sieve was reduced.

(2) ZSM-5 molecular sieve is prepared according to the method of the present invention, and the raw material of the reaction mixture does not contain solvent and sodium hydroxide. The method can improve the utilization rate of the molecular sieve synthesis equipment, reduce the production cost of the molecular sieve, and reduce the pollution in the production process of the molecular sieve.

(3) The ZSM-5 molecular sieve provided by the present invention has high crystallinity and nanocrystals, which can shorten the diffusion path of reactant and product molecules in the molecular sieve crystal and improve the catalytic production efficiency.

(4) Compared with the ZSM-5 molecular sieve synthesized by the traditional method, the ZSM-5 molecular sieve product prepared by the present invention contains a hierarchical pore structure.

Description of drawings

Fig. 1 is the X-ray diffraction (XRD) spectrum of ZSM-5 molecular sieve synthesized with rice husk ash as raw material in Example 1 of the present invention.

Fig. 2 is a flow chart of a method for preparing ZSM-5 molecular sieve from solid waste according to the present invention.

Detailed ways

The technical solutions of the present invention will be further described below with reference to specific embodiments.

A method of utilizing solid waste to prepare ZSM-5 molecular sieve of the present invention specifically comprises the following steps:

Step 1: take the solid waste as the silicon source, mix the silicon source, sodium carbonate decahydrate, aluminum source material and template agent according to a certain ratio, and mix and grind for 1-10 minutes;

Step 2: Put the mixture obtained in Step 1 into a stainless steel reactor, heat up to 100-200°C, and crystallize for 3-96 hours. After the crystallization is completed, rapidly cool, wash, and dry the filter cake to obtain a filter cake containing a hierarchical pore structure. ZSM-5 molecular sieve.

Further, the ratio of the silicon source, sodium carbonate decahydrate, aluminum source material and template agent is: n(TPABr)/n(SiO ₂ )=0.1-2.0; n(Na ₂ CO ₃ ·10H ₂ O)/n (SiO ₂ )=0.1 to 10; n(SiO ₂ )/n(Al ₂ O ₃ )=20 to +∞.

Further, the solid waste is rice husk ash, iron tailings or gold tailings. When iron tailings and gold tailings are used, the iron tailings and gold tailings need to be activated now.

Further, the activation treatment process is as follows: the gold tailings and the iron tailings are activated by means of alkali sintering, n(NaOH)/n(SiO ₂ )=1～4, the activation treatment temperature is 200～1000°C, and the activation The treatment time is 1 to 10 hours. The activated alkali sintered product is mixed with water and stirred for 50-70 minutes, the product is divided into water-soluble substances and water-insoluble solids, the solution pH is directly adjusted without separation of solid and liquid, and the solution is left standing for 6 to 24 hours at 80°C Dry at constant temperature to obtain solid powder.

Further, the composition of the iron tailings or gold tailings: the composition of the iron tailings or gold tailings mainly contains quartz, albite, potassium feldspar, anorthite, magnetite, pyrite, and cordier. Bluestone, talc and illite, the content of silicate in the iron tailings or gold tailings is not less than 50%.

Further, the iron tailings and gold tailings are not subjected to acid leaching and purification treatment before activation, so as to avoid the generation of acid-containing waste liquid.

Further, the ZSM-5 molecular sieve with the hierarchical pore structure can also be used as a seed crystal of the ZSM-5 molecular sieve.

Example 1:

Take 200 mesh rice husk ash as raw material, take 2 g of rice husk ash, add 0.2 g of sodium aluminate, 2.5 g of Na ₂ CO ₃ ·10H ₂ O and 0.2 g of TPABr in turn, place it in a mortar and grind and mix for 5 minutes, and the mixture is mixed. It was placed in a sealed stainless steel reaction kettle and heated to 100°C for 72 hours at a constant temperature for crystallization. After the crystallization, the filter cake was rapidly cooled, washed and dried to obtain a crystallized product. The X-ray diffraction (XRD) test shows that the product belongs to ZSM-5 molecular sieve. The crystal size of ZSM-5 molecular sieve is 40-200 nm. The Fe and Mn impurities in the raw material enter the molecular sieve framework. The obtained ZSM-5 molecular sieve product contains both micropores and mesoporous. Its XRD phase diagram is shown in Figure 1.

Example 2:

Using iron tailings as raw materials, the _SiO2 content is 67%, take 10 g of iron tailings and activate them in a muffle furnace at 500 ° C for 3 hours, immerse the activation product in water for 1 hour, adjust the pH of the filtrate to 9, stand for 12 hours, and dry The powder was obtained as the raw material for ZSM-5 molecular sieve synthesis. 2g of filter residue, 0.2g of sodium aluminate, 2.5g of Na ₂ CO ₃ ·10H ₂ O and 0.2g of TPABr were placed in a mortar and mixed for 5 minutes. Set to crystallize for 72 hours. After the crystallization is completed, the filter cake is rapidly cooled, washed and dried to obtain a crystallization product. The crystal size of ZSM-5 molecular sieve is 40-200 nm. Pores and Mesopores. The XRD results are the same as those of the first embodiment.

Example 3:

Using iron tailings as raw materials, the _SiO2 content is 67%, take 10 g of iron tailings and activate them in a muffle furnace at 500 ° C for 3 hours, immerse the activation product in water for 1 hour, adjust the pH of the filtrate to 9, stand for 12 hours, and dry The powder was obtained as the raw material for ZSM-5 molecular sieve synthesis. 2g of filter residue, 0.2g of sodium aluminate, 2.5g of Na ₂ CO ₃ ·10H ₂ O and 0.2 g of ZSM-5 molecular sieve obtained in Embodiment 1 were placed in a mortar for grinding and mixing for 5 minutes, and the mixture was placed in a sealed stainless steel reactor. The temperature was raised to 100°C in a constant temperature and allowed to stand for 72 hours for crystallization. After the crystallization is completed, the filter cake is rapidly cooled, washed and dried to obtain a crystallization product. The crystal size of ZSM-5 molecular sieve is 40-200 nm. Pores and Mesopores. The XRD results are the same as those of the first embodiment.

Example 4:

Using gold tailings as raw materials, the _SiO2 content is 71%, take 10 g of iron tailings and activate them in a muffle furnace at 500 ° C for 3 hours, immerse the activation product in water for 1 hour, adjust the pH of the filtrate to 9, stand for 12 hours, and dry The powder was obtained as the raw material for ZSM-5 molecular sieve synthesis. 3g of filter residue, 0.2g of sodium aluminate, 3g of Na ₂ CO ₃ ·10H ₂ O and 0.2g of TPABr were placed in a mortar and mixed for 5 minutes. Crystallize for 72 hours. After the crystallization is completed, the filter cake is rapidly cooled, washed and dried to obtain a crystallization product. The crystal size of ZSM-5 molecular sieve is 40-200 nm. Pores and Mesopores. The XRD results are the same as those of the first embodiment.

Example 5:

Using gold tailings as raw materials, the _SiO2 content is 71%, take 10 g of iron tailings and activate them in a muffle furnace at 500 ° C for 3 hours, immerse the activation product in water for 1 hour, adjust the pH of the filtrate to 9, stand for 12 hours, and dry The powder was obtained as the raw material for ZSM-5 molecular sieve synthesis. 3g of filter residue, 0.2g of sodium aluminate, 3g of Na ₂ CO ₃ ·10H ₂ O and 0.2g of ZSM-5 molecular sieve obtained in Embodiment 1 were placed in a mortar for grinding and mixing for 5 minutes, and the mixture was placed in a sealed stainless steel reactor. The temperature was raised to 100°C and the temperature was kept for crystallization for 72 hours. After the crystallization is completed, the filter cake is rapidly cooled, washed and dried to obtain a crystallization product. The crystal size of ZSM-5 molecular sieve is 40-200 nm. Pores and Mesopores. The XRD results are the same as those of the first embodiment.

Claims (5)

1. A method for preparing a ZSM-5 molecular sieve by using solid wastes specifically comprises the following steps:

step 1: mixing a silicon source, sodium carbonate decahydrate, an aluminum source substance and a template agent according to a certain proportion by taking solid waste as the silicon source, and mixing and grinding for 1-10 minutes; wherein the solid waste is rice hull ash, iron tailings or gold tailings; wherein the silicon source, the sodium carbonate decahydrate, the aluminum source and the template agent are in the following proportion: n (TPABr)/n (SiO)₂)=0.1~2.0；n(Na₂CO₃∙10H₂O)/n(SiO₂)=0.1~10；n(SiO₂)/n(Al₂O₃)=20~+∞；

Step 2: and (3) placing the mixture obtained in the step (1) into a stainless steel reaction kettle, heating to 100-200 ℃, crystallizing for 3-96 hours, and after the crystallization is finished, rapidly cooling, washing and drying a filter cake to obtain the ZSM-5 molecular sieve containing the hierarchical pore structure.

2. The method of claim 1, wherein when iron tailings and gold tailings are used as the silicon source, the iron tailings and the gold tailings are activated.

3. The method according to claim 2, wherein the activation treatment process is: activating gold tailings and iron tailings by adopting an alkali sintering mode, wherein n (NaOH)/n (SiO)₂) 1-4, the activation treatment temperature is 200-1000 ℃, and the activation treatment time is 1-10 hours; and mixing and stirring the activated alkali sintering product with water for 50-70 minutes, separating the product into a water-soluble substance and a water-insoluble solid, directly adjusting the pH =9 of the solution without solid-liquid separation, standing for 6-24 hours, and drying at the constant temperature of 80 ℃ to obtain solid powder.

4. The process according to claim 2, wherein the iron or gold tailings have a composition: the iron tailings or the gold tailings mainly contain quartz, albite, potash feldspar, anorthite, magnetite, pyrite, cordierite, talc and illite.

5. The method according to claim 2, characterized in that the iron tailings and the gold tailings are not subjected to acid leaching purification treatment before activation, so that acid-containing waste liquid is avoided.

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